1. Field of the Invention
This application relates to an improved 9 millimeter cartridge casing. More particularly, the inner bore contains at least two inflection points that facilitate deep drawing the cartridge casing from a brass cup.
2. Description of Related Art
A standard 9 millimeter cartridge casing has a typical length of 19 mm. To increase the power of a round, manufacturers have lengthened the casing up to 23 mm. One 9.times.23 mm cartridge casing is disclosed in U.S. Pat. No. 5,187,324 to Ricco, Sr. that is incorporated by reference in its entirety herein.
The Ricco, Sr. cartridge casing has a first portion, housing a powder charge and a bullet, with an outside diameter that decreases from a closed end of the portion to an open end. The inside diameter of the first portion increases from the closed end to a mid-point and then is essentially constant from the mid-point to the open end.
While the increased length of the 9.times.23 mm cartridge casing provides an increase in the volume of the power charge and an increase in the firing power of the round, the increased length of the casing wall causes problems with manufacture. The casing fractures at the inflection point in the inner bore of the first portion.
There exists, therefore, a need for an increased length 9 millimeter cartridge casing that is suitable for deep drawing manufacture.